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March 28, 2011 (Anaheim, Calif.) -- Nicotine appears to be the main culprit responsible for high blood sugar levels in smokers with diabetes, according to new research presented here at the annual meeting of the American Chemical Society.

Those constantly high blood sugar levels, in turn, increase the risk of serious diabetes complications such as heart attack, stroke, kidney failure, and nerve damage.

''If you have diabetes and if you are a smoker, you should be concerned about this," says Xiao-Chuan Liu, PhD, a researcher at California State Polytechnic University in Pomona, who spoke about his findings at a news conference Sunday.

In his laboratory study, he exposed human blood samples to nicotine. The nicotine raised the level of hemoglobin A1c, a measure of blood sugar control. The higher the nicotine dose, the more the A1c level rose.

For years, doctors have known that smokers who have diabetes tend to have poorer blood sugar control than nonsmokers with diabetes.

However, until Liu's study, he says, no one could say for sure which of the more than 4,000 chemicals in cigarette smoke was responsible.

About 26 million people in the U.S. have diabetes, according to the American Diabetes Association, although 7 million of those are undiagnosed.

Nicotine Raises Blood Sugar: Study Details

Liu took red blood cells from people and treated them in the laboratory with glucose and nicotine at various concentrations.

To measure the effects of the nicotine on the levels of blood sugar, he used the hemoglobin A1c blood test. This test measures the average blood sugar control for the previous three months or so.

The higher the test results, the more uncontrolled the blood sugar is.

Liu used doses of nicotine comparable to what would be found in the blood of smokers. The levels of nicotine he used in the lab would correspond roughly to the exposure a smoker would get by smoking one or two packs a day, he says.

He found that the nicotine raised the HbA1c level by nearly 9% to up to 34.5%, depending on nicotine exposure.

The study was funded internally, Liu says.

Nicotine and Blood Sugar: Second Opinion

The study results about nicotine and blood sugar make sense, says Peter Galier, MD, attending physician and former chief of staff at Santa Monica--UCLA Medical Center & Orthopaedic Hospital. "I was always under the impression that nicotine was the culprit," Galier says. He reviewed the study findings for WebMD.

''What the study is telling us is that nicotine is most likely the reason smokers have elevated HbA1c levels," says Galier, an associate professor of medicine at the University of California Los Angeles David Geffen School of Medicine.

Caveat About Nicotine Replacement Products

Ideally, Liu says, doctors will use the new study results to encourage patients with diabetes to stop smoking cigarettes. But he warns that smokers shouldn't use the smoking cessation products that contain nicotine, such as the nicotine patches, long-term because of their effects on blood sugar.

He couldn't pinpoint an ideal maximum time for using such products.

Makers of nicotine patches suggest that smokers use patches of progressively declining strengths as they wean themselves from cigarettes.

Galier encourages short-term use of the nicotine replacement products. "I usually recommend using each strength for two to four weeks," he tells WebMD. With a three-step program, people ideally stay on the product only for 6 to 12 weeks, he says.

This study was presented at a medical conference. The findings should be considered preliminary as they have not yet undergone the "peer review" process, in which outside experts scrutinize the data prior to publication in a medical journal.